Lipidomic and Ultrastructural Characterization of the Cell Envelope of <named-content content-type="genus-species">Staphylococcus aureus</named-content> Grown in the Presence of Human Serum

ABSTRACT Staphylococcus aureus can incorporate exogenous straight-chain unsaturated and saturated fatty acids (SCUFAs and SCFAs, respectively) to replace some of the normally biosynthesized branched-chain fatty acids and SCFAs. In this study, the impact of human serum on the S. aureus lipidome and c...

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Autores principales:	Kelly M. Hines, Gloria Alvarado, Xi Chen, Craig Gatto, Antje Pokorny, Francis Alonzo, Brian J. Wilkinson, Libin Xu
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	lipidomics human serum lipids fatty acid incorporation lipid association cell envelope structure Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/b40cd8a180f147d986720f52a69a8884
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spelling	oai:doaj.org-article:b40cd8a180f147d986720f52a69a88842021-11-15T15:30:15ZLipidomic and Ultrastructural Characterization of the Cell Envelope of <named-content content-type="genus-species">Staphylococcus aureus</named-content> Grown in the Presence of Human Serum10.1128/mSphere.00339-202379-5042https://doaj.org/article/b40cd8a180f147d986720f52a69a88842020-06-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mSphere.00339-20https://doaj.org/toc/2379-5042ABSTRACT Staphylococcus aureus can incorporate exogenous straight-chain unsaturated and saturated fatty acids (SCUFAs and SCFAs, respectively) to replace some of the normally biosynthesized branched-chain fatty acids and SCFAs. In this study, the impact of human serum on the S. aureus lipidome and cell envelope structure was comprehensively characterized. When S. aureus was grown in the presence of 20% human serum, typical human serum lipids, such as cholesterol, sphingomyelin, phosphatidylethanolamines, and phosphatidylcholines, were present in the total lipid extracts. Mass spectrometry showed that SCUFAs were incorporated into all major S. aureus lipid classes, i.e., phosphatidylglycerols, lysyl-phosphatidylglycerols, cardiolipins, and diglucosyldiacylglycerols. Heat-killed S. aureus retained fewer serum lipids and failed to incorporate SCUFAs, suggesting that association and incorporation of serum lipids with S. aureus require a living or nondenatured cell. Cytoplasmic membranes isolated from lysostaphin-produced protoplasts of serum-grown cells retained serum lipids, but washing cells with Triton X-100 removed most of them. Furthermore, electron microscopy studies showed that serum-grown cells had thicker cell envelopes and associated material on the surface, which was partially removed by Triton X-100 washing. To investigate which serum lipids were preferentially hydrolyzed by S. aureus lipases for incorporation, we incubated individual serum lipid classes with S. aureus and found that cholesteryl esters (CEs) and triglycerides (TGs) are the major donors of the incorporated fatty acids. Further experiments using purified Geh lipase confirmed that CEs and TGs were the substrates of this enzyme. Thus, growth in the presence of serum altered the nature of the cell surface with implications for interactions with the host. IMPORTANCE Comprehensive lipidomics of S. aureus grown in the presence of human serum suggests that human serum lipids can associate with the cell envelope without being truly integrated into the lipid membrane. However, fatty acids derived from human serum lipids, including unsaturated fatty acids, can be incorporated into lipid classes that can be biosynthesized by S. aureus itself. Cholesteryl esters and triglycerides are found to be the major source of incorporated fatty acids upon hydrolysis by lipases. These findings have significant implications for the nature of the S. aureus cell surface when grown in vivo. Changes in phospholipid and glycolipid abundances and fatty acid composition could affect membrane biophysics and function and the activity of membrane-targeting antimicrobials. Finally, the association of serum lipids with the cell envelope has implications for the physicochemical nature of the cell surface and its interaction with host defense systems.Kelly M. HinesGloria AlvaradoXi ChenCraig GattoAntje PokornyFrancis AlonzoBrian J. WilkinsonLibin XuAmerican Society for Microbiologyarticlelipidomicshuman serum lipidsfatty acid incorporationlipid associationcell envelope structureMicrobiologyQR1-502ENmSphere, Vol 5, Iss 3 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	lipidomics human serum lipids fatty acid incorporation lipid association cell envelope structure Microbiology QR1-502
spellingShingle	lipidomics human serum lipids fatty acid incorporation lipid association cell envelope structure Microbiology QR1-502 Kelly M. Hines Gloria Alvarado Xi Chen Craig Gatto Antje Pokorny Francis Alonzo Brian J. Wilkinson Libin Xu Lipidomic and Ultrastructural Characterization of the Cell Envelope of <named-content content-type="genus-species">Staphylococcus aureus</named-content> Grown in the Presence of Human Serum
description	ABSTRACT Staphylococcus aureus can incorporate exogenous straight-chain unsaturated and saturated fatty acids (SCUFAs and SCFAs, respectively) to replace some of the normally biosynthesized branched-chain fatty acids and SCFAs. In this study, the impact of human serum on the S. aureus lipidome and cell envelope structure was comprehensively characterized. When S. aureus was grown in the presence of 20% human serum, typical human serum lipids, such as cholesterol, sphingomyelin, phosphatidylethanolamines, and phosphatidylcholines, were present in the total lipid extracts. Mass spectrometry showed that SCUFAs were incorporated into all major S. aureus lipid classes, i.e., phosphatidylglycerols, lysyl-phosphatidylglycerols, cardiolipins, and diglucosyldiacylglycerols. Heat-killed S. aureus retained fewer serum lipids and failed to incorporate SCUFAs, suggesting that association and incorporation of serum lipids with S. aureus require a living or nondenatured cell. Cytoplasmic membranes isolated from lysostaphin-produced protoplasts of serum-grown cells retained serum lipids, but washing cells with Triton X-100 removed most of them. Furthermore, electron microscopy studies showed that serum-grown cells had thicker cell envelopes and associated material on the surface, which was partially removed by Triton X-100 washing. To investigate which serum lipids were preferentially hydrolyzed by S. aureus lipases for incorporation, we incubated individual serum lipid classes with S. aureus and found that cholesteryl esters (CEs) and triglycerides (TGs) are the major donors of the incorporated fatty acids. Further experiments using purified Geh lipase confirmed that CEs and TGs were the substrates of this enzyme. Thus, growth in the presence of serum altered the nature of the cell surface with implications for interactions with the host. IMPORTANCE Comprehensive lipidomics of S. aureus grown in the presence of human serum suggests that human serum lipids can associate with the cell envelope without being truly integrated into the lipid membrane. However, fatty acids derived from human serum lipids, including unsaturated fatty acids, can be incorporated into lipid classes that can be biosynthesized by S. aureus itself. Cholesteryl esters and triglycerides are found to be the major source of incorporated fatty acids upon hydrolysis by lipases. These findings have significant implications for the nature of the S. aureus cell surface when grown in vivo. Changes in phospholipid and glycolipid abundances and fatty acid composition could affect membrane biophysics and function and the activity of membrane-targeting antimicrobials. Finally, the association of serum lipids with the cell envelope has implications for the physicochemical nature of the cell surface and its interaction with host defense systems.
format	article
author	Kelly M. Hines Gloria Alvarado Xi Chen Craig Gatto Antje Pokorny Francis Alonzo Brian J. Wilkinson Libin Xu
author_facet	Kelly M. Hines Gloria Alvarado Xi Chen Craig Gatto Antje Pokorny Francis Alonzo Brian J. Wilkinson Libin Xu
author_sort	Kelly M. Hines
title	Lipidomic and Ultrastructural Characterization of the Cell Envelope of <named-content content-type="genus-species">Staphylococcus aureus</named-content> Grown in the Presence of Human Serum
title_short	Lipidomic and Ultrastructural Characterization of the Cell Envelope of <named-content content-type="genus-species">Staphylococcus aureus</named-content> Grown in the Presence of Human Serum
title_full	Lipidomic and Ultrastructural Characterization of the Cell Envelope of <named-content content-type="genus-species">Staphylococcus aureus</named-content> Grown in the Presence of Human Serum
title_fullStr	Lipidomic and Ultrastructural Characterization of the Cell Envelope of <named-content content-type="genus-species">Staphylococcus aureus</named-content> Grown in the Presence of Human Serum
title_full_unstemmed	Lipidomic and Ultrastructural Characterization of the Cell Envelope of <named-content content-type="genus-species">Staphylococcus aureus</named-content> Grown in the Presence of Human Serum
title_sort	lipidomic and ultrastructural characterization of the cell envelope of <named-content content-type="genus-species">staphylococcus aureus</named-content> grown in the presence of human serum
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/b40cd8a180f147d986720f52a69a8884
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Lipidomic and Ultrastructural Characterization of the Cell Envelope of <named-content content-type="genus-species">Staphylococcus aureus</named-content> Grown in the Presence of Human Serum

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